Compressible heart valve annulus sizing templates

ABSTRACT

Compressible heart valve annulus sizing templates suitable for minimally-invasive or otherwise reduced accessibility surgeries. The sizing templates may be folded, rolled, or otherwise compressed into a reduced configuration for passage through an access tube or other such access channel. Once expelled from the access tube the sizing templates expand to their original shape for use in sizing the annulus. The templates may be formed of an elastomeric polymer material such as silicone, a highly elastic metal such as NITINOL, or both. Grasping tabs or connectors for handles permit manipulation from outside the body. A NITINOL wireform may be compressed for passage through an access tube and expelled from the distal end thereof into a cloth cover to assume a sizer shape.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/429,123, filed Mar. 23, 2012, now U.S. Pat. No. 11,213,393, whichclaims the benefit of U.S. Application No. 61/470,658, filed Apr. 1,2011, the entire disclosures all of which are incorporated by referencefor all purposes.

FIELD OF THE INVENTION

The present invention generally relates to anatomical orifice sizersand, more particularly, to sizing templates for heart valve annulusesthat may be deployed through access devices, and methods of use.

BACKGROUND OF THE INVENTION

In vertebrate animals, the heart is a hollow muscular organ having fourpumping chambers: the left and right atria and the left and rightventricles, each provided with its own one-way valve. The natural heartvalves are identified as the aortic, mitral (or bicuspid), tricuspid andpulmonary, each having flexible flow-occluding leaflets mounted to asurrounding annulus comprising dense fibrous rings that attach eitherdirectly or indirectly to the atrial and ventricular muscle fibers. Eachannulus defines a flow orifice.

Heart valve disease is a widespread condition in which one or more ofthe valves of the heart fails to function properly. Diseased heartvalves may be categorized as either stenotic, wherein the valve does notopen sufficiently to allow adequate forward flow of blood through thevalve, and/or incompetent, wherein the valve does not close completely,causing excessive backward flow of blood or regurgitation through thevalve when the leaflets are supposed to coapt together. Valve diseasecan be severely debilitating and even fatal if left untreated.

Various surgical techniques may be used to repair a diseased or damagedvalve. In a valve replacement operation, the damaged leaflets areexcised and the annulus sculpted to receive a replacement valve. Anotherless drastic method for treating defective valves is through repair orreconstruction, which is typically used on minimally calcified valves.One repair technique that has been shown to be effective in treatingincompetence is annuloplasty, in which the deformed valve annulus isreshaped by attaching a prosthetic annuloplasty repair segment or ringto the valve annulus. The annuloplasty ring is designed to support thefunctional changes that occur during the cardiac cycle: maintainingleaflet coaptation and valve integrity to prevent regurgitation whilepermitting good hemodynamics during forward flow.

To perform successful valve replacement and annuloplasty surgeries, thesize of the valve annulus must be accurately measured. Sizing may beachieved by measuring the width and the height of the anterior leafletof the mitral valve, for example, using a valve sizer or template, whichresembles the shape of the valve annulus and is provided in variousincremental sizes corresponding to the stepped valve or ring sizes. Inorder to use a sizing template, a surgeon estimates the valve annulussize and selects the template accordingly. The template is guided intoproximity of the annulus with a handle. If the template is not judged tobe the correct size, it is withdrawn, and replaced by a differenttemplate. Once the size of the annulus has been determined, a properlysized valve or annuloplasty device may be selected and implanted.

Surgical techniques for annuloplasty surgery are typically performedopen-chest. This usually requires the patient to be placed on a cardiacbypass machine to pump and oxygenate the blood while the surgeonoperates on the stopped heart muscle. Open-chest surgery can be verytraumatic for the patient and recovery can take many months.Additionally, such surgery may not be an option for some patients due tolimited possibility for recovery, concurrent disease, or age.

In recent years, advancements in “minimally-invasive” surgery andinterventional cardiology have encouraged some investigators to pursuedirect access port surgeries and percutaneous replacement of heartvalves. Similarly, less invasive annuloplasty implant procedures havebeen developed. However, these procedures reduce the available space todeliver surgical instruments to a surgical site, and reduce the space inwhich surgical instruments may be operated within the area of thesurgical site. Traditional annuloplasty and valve sizing and holdinginstruments are designed for use with open-chest surgery that exposesthe implant site. Such instruments will not fit through significantlyreduced surgical field access points or passages. Some valve sizingtemplates for less invasive procedures have been disclosed, includingthose in U.S. Patent Publication No. 2009/0192602 to Kuehn, et al.

Despite the current existence of sizing devices for sizing a valveannulus, there is still a need for improved devices, and in particularthose devices that may be used during less-invasive cardiac surgicalprocedures.

SUMMARY OF THE INVENTION

In accordance with a first embodiment, the present application presentsa heart valve annulus sizing template comprising a compressible bodyhaving a peripheral plan view shape of a target heart valve annulus anda thickness between about 0.3-3.0 mm. An inner skeleton is embeddedwithin the compressible body and is formed of a material more rigid thanthe material of the compressible body. The inner skeleton may comprisean outer peripheral ring in plan view shaped like a target heart valveannulus and a plurality of spokes extending inward therefrom. Thecompressible body may be elastomeric, such as silicone, or an inelasticpolymer. In one embodiment, the compressible body comprises a solidmember extending across the periphery thereof.

Another aspect of the application is a heart valve annulus sizingtemplate comprising a solid compressible body having a peripheral planview shape of a target heart valve annulus and a thickness between about0.3-3.0 mm. The sizing template further includes an inner fabricreinforcement member embedded within the compressible body. The templatemay also have a fabric grasping tab projecting away from one side of thecompressible body integrally formed with the inner fabric reinforcementmember. Alternatively, the template has a grasping tab integrally moldedwith and projecting away from one side of the compressible body.Preferably, the compressible body is plate-like member having aperiphery sized to approximate the mitral annulus, and the inner fabricreinforcement member is generally planar and sized slightly smaller thanthe plate-like member.

Another heart valve annulus sizing template disclosed herein includes anelastomeric, compressible body having an outer peripheral ring in planview shaped like a target heart valve annulus and a plurality of spokesextending inward therefrom to define visibility windows through thecompressible body. A central hub is provided to which the spokesconnect. The peripheral ring may be shaped to match the shape of themitral annulus with a convex posterior side opposite a relativelystraight or less convex anterior side, and wherein there are two spokesthat generally project toward trigone corners between the posterior andanterior sides. The material of the compressible body is desirablytransparent and includes a highly visible marker line circumscribing theouter peripheral ring. In one version, the highly visible marker line iscolor-coded depending on the size of annulus being measured.

A still further heart valve annulus sizing template of the presentapplication comprises a compressible elastic wireform having an expandedshape of a target valve annulus and a compressed shape of smallerprofile. An access tube is provided through which the wireform in itscompressed shape may be advanced. The template further has a cloth coverattached to a distal end of the access tube and having an inner volumeand shape that closely receives the wireform in its expanded shape. Theexpanded shape of the wireform may conform to a mitral annulus such thatit has a convex posterior side opposite a relatively straight or lessconvex anterior side. The expanded shape of the wireform further mayinclude a pair of trigone notches at the intersections of the posteriorand anterior sides, wherein the wireform is darkly colored to contrastwith a light colored cloth cover.

The present application also discloses a method of sizing a heart valveannulus comprising first providing a compressible annulus sizingtemplate including an elastomeric body in the shape of a target valveannulus. The annulus sizing template is passed through a constrictor toreduce its profile, and constrained in its reduced profileconfiguration. The reduced profile annulus sizing template is thenadvanced to a target annulus, whereupon the constraints are released sothat the annulus sizing template expands to an original shape. Finally,the annulus sizing template in its expanded configuration is manipulatedto size the target valve annulus.

A further method of sizing a heart valve annulus disclosed hereincomprises providing a foldable annulus sizing template including anelastomeric body in the shape of a target valve annulus. A technicianfolds the annulus sizing template to reduce its profile, and constrainsthe annulus sizing template in its reduced profile configuration. Thereduced profile annulus sizing template is then advanced to a targetannulus, whereupon the constraints are released so that the annulussizing template expands to an original shape. Finally, the annulussizing template in its expanded configuration is manipulated to size thetarget valve annulus. In one embodiment, the foldable annulus sizingtemplate has a shape in plan view of a mitral valve annulus, and furtherincludes fold lines provided thereon generally parallel to a major axisof the sizing template.

Another method of sizing a heart valve annulus includes providing acompressible annulus sizing template including an elastic wireformhaving a distal end in the shape of a target valve annulus. A technicianpasses the elastic wireform into an access tube to reduce its profile,and then advances the reduced profile elastic wireform to a targetannulus. The distal end of the elastic wireform is expelled from theaccess tube into a surrounding cloth cover such that the distal endexpands and assumes its original shape of the target valve annuluswithin the cloth cover. Finally, the annulus sizing template in itsexpanded configuration is manipulated to size the target valve annulus.The cloth cover is desirably secured to a distal end of the access tube.

A further understanding of the nature and advantages of the presentinvention are set forth in the following description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained and other advantages and featureswill appear with reference to the accompanying schematic drawingswherein:

FIG. 1A is a plan view of an exemplary flexible annuloplasty ring sizingtemplate of the present application, and FIGS. 1B and 1C illustrate thetemplate folded into a smaller delivery profile;

FIG. 2A shows a folded flexible annuloplasty ring sizing template heldtogether with a clip, and FIG. 2B shows the clipped template placewithin an access tube;

FIG. 3A is a plan view of an alternative flexible annuloplasty ringsizing template of the present application, and FIGS. 3B and 3Cillustrate the template rolled into a smaller delivery profile andplaced within an access tube;

FIG. 4 illustrates one method for compressing a flexible annuloplastyring sizing template into a smaller profile for introduction within anaccess tube;

FIG. 5 shows a rolled annuloplasty ring sizing template wrapped around adelivery handle and held with a strap;

FIGS. 6A-6C are various views of an alternative flexible annuloplastyring sizing template comprising a compressible wireform surrounded by acloth cover being expelled from a distal end of an access tube;

FIG. 7A is a perspective view of a still further flexible annuloplastyring sizing template of the present application formed of an elastomericmaterial and having visibility windows, and FIG. 7B is a schematic viewof the sizing template being extruded through a compression cone;

FIG. 8 is a perspective view of a solid elastomeric annuloplasty ringsizing template having an internal more rigid skeleton;

FIG. 9 is a sizing template similar to that shown in FIG. 8 and having agrasping tab extending from one face thereof; and

FIG. 10 is a perspective view of a solid annuloplasty ring sizingtemplate having an internal fabric reinforcement member and a fabricgrasping tab extending from one face thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention include heart valve annulus sizingtemplates, and attendant delivery devices that are made, configuredand/or may be manipulated to fit through significantly reduced surgicalfield access points and may be used in reduced surgical fields ofoperation. In particular, the sizing templates are deformable such thatthe devices may deform, bend or flex in order to fit through reducedsurgical field access points. The sizing templates are preferably madeto be attached and detached from the delivery devices of the presentinvention, however they may also be permanently attached thereto.Furthermore, heart valve surgeries carried out through reduced sizeaccess channels may benefit greatly from the assistance of roboticmanipulators. The templates of the present invention are particularlywell-suited to be passed through access passages and manipulated usingrobotic graspers and the like.

The sizing templates and delivery devices will be discussed with regardto their use during annuloplasty surgery. During annuloplasty surgery,the purpose of the delivery device is to first deliver a sizing templateto a valve annulus that is in need of repair in order to size theannulus, and then after removal of the sizing template from the body, aholder with an attached annuloplasty ring is advanced and anchored tothe valve annulus. Although the present application addressesannuloplasty surgery, it is contemplated that the present invention orfeatures thereof may be used during other minimally invasive surgicalprocedures as well.

It should be understood that the various materials, shapes, andconfigurations of all the sizing templates described herein may beinterchangeable. For example, a description of a ball and socket handleconnection below may be transferred to other templates than the one forwhich it is described. Likewise, unless mutually exclusive, any of thedelivery methodologies described herein may be utilized for each of thetemplates with similar results.

FIG. 1A shows a first exemplary flexible annuloplasty ring sizingtemplate 20 of the present application in plan view. As seen in FIGS. 1Band 1C, the template 20 has a relatively small thickness and isflexible. The template 20 defines a modified D-shape mimicking thenormal outline of a mitral annulus. It is the mitral valve that mostoften requires repair, but it should be understood that the presenttemplates may be used to size other of the heart's annuluses, such asthe tricuspid annulus. In the illustrated embodiment, the template 20includes a convex posterior edge 22 that extends approximatelythree-quarters around the entire periphery and is delineated by a pairof trigone-marking notches 24. The posterior edge 22 matches theposterior aspect of the mitral annulus. The rest of the peripheral edgeof the template 20, or anterior edge 26, forms an uneven somewhatconcave shape that matches the anterior aspect of the mitral annulus. Ina preferred embodiment, the plan view size of the template 20 conformsto the size of traditional sizers for annuloplasty rings where the majoraxis ranges between about 24 mm to about 40 mm. The thickness of thetemplate 20 desirably ranges between about 0.3-3.0 millimeters, whichmay depend on the material, preferably silicone.

FIG. 1A indicates in phantom a pair of parallel fold lines 28 alongwhich the template 20 may be folded as indicated in FIGS. 1B and 1C. Thefold lines 28 may be perforations or other indentations to ensurefolding along those lines, or may be simply marked on the surface of thetemplate 20 to assist a technician when collapsing the template. Ingeneral, the template 20 is folded along one or more lines parallel toits major axis, which extends across the widest dimension of the planview. In the illustrated embodiment, the template 20 is collapsed byfolding twice so as to have three flaps that lie against one another, asseen in the view of FIG. 1C. Additionally, a suture thread 30 anchoredto an eyelet 32 may be used to secure the template 20 in its foldedconfiguration. The eyelet 32 also provides an anchor for a deliveryhandle or other such grasper to manipulate the template 20 once in thebody and permitted to expand.

In use, a technician folds the template 20 into its reduced profileconfiguration of FIGS. 1B and 1C, and then inserts the template into anaccess tube or other such vehicle. The delivery tube enters the bodythrough a direct access aperture, such as through a port formed in thechest directly over the heart. Alternatively, the surgery may require amini thoracotomy which is more invasive than ports but less invasivethan a full thoracotomy (open-heart procedure). Using forceps or aspecial grasper (not shown), the folded template 20 passes through theaccess tube and is expelled therefrom adjacent the mitral annulus. Atthis point, the flexibility of the material of the template 20 causes itto expand once released from the access tube, and after severing thesecuring suture thread 30, if present. Using the aforementioned forcepsor grasper, the surgeon then manipulates the template 20 into properposition within the mitral annulus and determines the size of theannulus relative thereto. If necessary, the template 20 is removed fromthe surgical site, and a differently sized template introduced for moreaccuracy.

The sizing template 20 (as well as any other templates described herein)is preferably made from biocompatible material that is flexible ordeformable. The flexible material is also preferably opticallytransparent, but could also be opaque. Some particular materials thatmay be used include a number of polymers and elastomers, including, butnot limited to, polyurethanes and silicones. The flexible material maybe compounded with a ferrous metal to achieve magnetic properties or anyother radiopaque material for identification under x-ray. Also, thematerial could comprise a shape memory polymer or metal, such asNITINOL, for example. Other similar materials having such similarproperties are also contemplated by the present invention. The materialis preferably able to regain its predefined shape after being deformedin some way.

FIG. 2A shows the folded flexible annuloplasty ring sizing template 20held together with a clip 34, rather than a suture. The clip 34 may betethered to suture (not shown), and may be provided in a variety ofconfigurations, including a clothespin-type as shown, or a simple U clipthat fits closely around the outside of the folded contour. FIG. 2Bshows the clipped template 20 place within an access tube 36 fordelivery to the implantation site.

FIG. 3A illustrates an alternative flexible annuloplasty ring sizingtemplate 40 of the present application, and FIGS. 3B and 3C illustratethe template spirally rolled into a smaller delivery profile and placedwithin an access tube 42. The template 40 may be configured the same asthe earlier-describe template 20, without any particular fold linesdelineated. The rolled template 40 may also be held in its constrictedconfiguration with sutures or a clip, as described above.

FIG. 4 illustrates one method for compressing the flexible annuloplastyring sizing template 40 into a smaller profile for introduction withinthe access tube 42. In particular, the flat template 40 is guidedlengthwise into a funnel or cone-shaped constrictor 44 which causes theflexible template to bend and then eventually to curl into a spiralshape. By sizing a narrow end 46 of the constrictor 44 the same as orslightly smaller than the access tube 42, the template then can beinserted within the access tube in its spiral configuration. Thematerial of the constrictor 44 may be lubricious, such as Teflon, or theinterior of the constrictor may be coated with a lubriciousbiocompatible material such as used to facilitate passage of intraocularlenses through delivery syringes.

FIG. 5 illustrates an annuloplasty ring sizing template 50 rolled into atube or spiral and wrapped around a delivery handle 52. The rolledtemplate 50 is secured on the handle 52 using a strap 54 having Velcroends, though one or more sutures may also be used. This assembly may beinserted into the body with or without using an access tube. Upondelivery of the distal end of the delivery handle 52 to a valve annulus,the surgeon releases the sizing template 50 by removing the strap 54 orcutting or removing sutures as applicable. A separate grasper or othersuch device may then be used to manipulate the sizing template 50 intothe proper orientation within the annulus for a sizing comparison. Inone embodiment, an edge of the sizing template 50 may be tethered to thedelivery handle 52 to avoid complete detachment of the template while atthe same time permitting it to freely move in and around the annulus.

FIGS. 6A-6C show a still further flexible annuloplasty ring sizingtemplate 60 comprising a compressible wireform 62 surrounded by a knitcloth cover 64. The cloth cover 64 attaches to a distal end of an accesstube 66 through the use of a suture 68 and eyelet 70, for example,though other attachment means are contemplated. The compressiblewireform 62 extends through the access tube 66 in a compressed,generally linear configuration (not shown) and is manipulatedlongitudinally from a proximal end thereof. Preferably, the wireform 62is formed of NITINOL. By expelling the wireform 62 from the distal endof the access tube 66, as shown in FIGS. 6B and 6C, the wireform 62expands and assumes its relaxed shape within the cloth cover 64. In apreferred embodiment, the sizing template 60 assumes a generally planarframe perpendicular to the axis of the access tube 66 and proximalportion of the wireform 62, as seen in FIG. 6C.

In the illustrated embodiment, the wireform 62 expands into the shape ofa mitral annulus sizing template, having a convex posterior side 72opposite a concave anterior side 74, and including a pair of optionaltrigone notches 76. Although the notches 76 are somewhat occluded by thecloth cover 64, the cover may be formed of a diaphanous material and thewireform 62 may be darkly colored or otherwise colored to contrast withthe cloth cover so as to be visible therethrough. Alternatively, thewireform 62 may be radiopaque such that the trigones 76 are visibleunder fluoroscopy. In any event, the sizing template 60 forms asubstantially solid-looking body to be more visible to the surgeon whenassessing the size of the surrounding mitral annulus.

In use, the surgeon inserts the access tube 66 into the body through anaccess port or mini thoracotomy such that its distal end is adjacent thetarget annulus, and then advances the linearly compressed wireform 62therethrough. The distal end of the wireform 62 expands within the clothcover 64 to form the properly shaped sizing template 60. After examiningthe fit of the sizing template 60 within the mitral annulus by directvisible examination or using a scope, the surgeon then retracts thewireform 62 back into the access tube 66, and removes the entireassembly. A second sizing procedure may be required with adifferently-sized template 60 if the surgeon so desires.

FIG. 7A is a perspective view of a still further flexible annuloplastyring sizing template 80 formed of an elastomeric material and havingvisibility windows 82. More particularly, the template 80 has theapproximate peripheral shape of a mitral annulus with an outer ringdefining a convex posterior side 84 and a relatively straight or lessconvex anterior side 86. Two or more linear spokes 88 extend inward fromthe outer ring of the template 80 to a generally central hub 90 to whicha handle or grasper 92 may be attached. Preferably two spokes 88 areutilized which point generally to the trigone area of the profile of themitral annulus, thus helping ensure proper orientation of the sizingtemplate 80 upon introduction to the target annulus area. The visibilitywindows 82 are defined in the spaces between the outer ring and thespokes 88. The material of the template 80 may be opaque or transparentfor greater visibility. If the template material is transparent, ahighly visible marker line circumscribing the outer periphery may beprovided. Furthermore, the marker line may be color-coded to differentsizes of annuluses. For instance, a 26 mm template may have a red markerline while a 28 mm template has a purple marker line, and so on.

FIG. 7B is a schematic view of the sizing template 80 being extrudedthrough a compression cone 94, much like the constrictor 44 describedabove. Although not shown, the sizing template 80 may be constricted toa reduced profile and passed into an access tube, or otherwise securedin its constricted configuration using a suture or other such device.

In use, once the sizing template 80 has been extruded out of the end ofan access tube, or otherwise released to assume its relaxedconfiguration at the target annulus, the handle or grasper 92 may beattached to the central hub 90 for manipulation purposes.

It should be understood that the central hub 90 may take a variety offorms so that different graspers can be connected thereto. For example,the hub 90 may be configured as a generally spherical socket to receivea ball end of a handle (not shown) in a snap-fit configuration to allowfor universal rotation of the template 80. In this configuration, thehub 90 may be made from a harder material, such as a harder polymer,then the remainder of the template 80 to permit a secure snap-fitconnection. Alternatively, an embedded metal ring around an opening ofthe hub 90 all the same material as the template 80 may be provided tofacilitate the snap-fit connection. Consequently, the hub 90 can bemounted on the remainder of the template 80 using adhesive, ultrasonicwelding, or other such attachment means.

FIG. 8 is a perspective view of a solid annuloplasty ring sizingtemplate 100 having an internal skeleton 102 embedded within and morerigid than a surrounding elastomeric template body 104. The skeleton 102may be formed of a highly elastic polymer or metal such as NITINOL sothat it can be compressed into a much smaller profile and advancedthrough an access tube. Because of the restoring force of the skeleton102, the template body 104 may be made of a material that is notelastomeric, but instead is merely compressible. However, the elasticityof the inner skeleton 102 permits the template body 104 to alternativelybe formed of a transparent non-elastic polymer material, such as aviscoelastic or photoviscoelastic polymeric material like plasticizedPolyvinyl Chloride,

In one embodiment, the skeleton 102 has a shape much like the sizingtemplate 80 of FIG. 7A, with an outer ring and spokes leading to acentral hub 106. As described above, the template 100 may be compressedusing a conical constrictor or other such device and held in itsconstricted configuration within an access tube, or using sutures, astrap or the like. Once expelled from the end of the access tube, orotherwise released, the template 100 assumes its relaxed configurationas seen in FIG. 8 . At this point, a handle 108 or other such graspermay be connected to the central hub 106 and used to manipulate thetemplate 100 to size the annulus.

FIG. 9 is a sizing template 110 similar to that shown in FIG. 8 buthaving a grasping tab 112 extending from one face thereof. The graspingtab 112 projects perpendicularly upward from the generally planar bodyof the template 110, and may be easily grasped with forceps or othersuch device, for example robotic end effectors. Preferably, the graspingtab 112 is integrally molded with the elastomeric portion of thetemplate 110. An inner skeleton 114 is shown by a cutaway portion of theelastomeric body 116.

Finally, FIG. 10 illustrates a solid annuloplasty ring sizing template120 having an internal fabric reinforcement member 122 embedded withinan elastomeric body 124. The elastomeric body 124 comprises a plate-likemember having a periphery sized to approximate the mitral annulus, andthe internal fabric reinforcement member 122 is generally planar andsized slightly smaller. A fabric grasping tab 126 extends from one faceof the elastomeric body 124 for manipulation by forceps or other suchgrasper. The grasping tab 126 may be integrally connected with thefabric reinforcement member 122 for strength.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription and not of limitation. Therefore, changes may be made withinthe appended claims without departing from the true scope of theinvention.

What is claimed is:
 1. A heart valve annulus sizing system, comprising:a compressible elastic wireform having an expanded shape of a targetheart valve annulus and a compressed shape of smaller profile; an accesstube through which the wireform in its compressed shape may be advanced;and a cloth cover attached to a distal end of the access tube and havingan inner volume and shape that closely receives the wireform in itsexpanded shape when advanced beyond the access tube.
 2. The system ofclaim 1, wherein the expanded shape of the wireform conforms to a mitralannulus and has a convex posterior side opposite a relatively straightor less convex anterior side.
 3. The system of claim 2, wherein theexpanded shape of the wireform further includes a pair of trigonenotches at the intersections of the posterior and anterior sides, andwherein the wireform is darkly colored to contrast with a light coloredcloth cover.
 4. The system of claim 2, wherein the wireform isradiopaque such that the trigones are visible under fluoroscopy.
 5. Thesystem of claim 1, wherein the wireform is configured to expand andassumes a shape within the cloth cover that is generally perpendicularto the axis of the access tube and to a proximal portion of the wireformthat remains within the access tube.
 6. The system of claim 1, whereinthe cloth cover is formed of a diaphanous material and the wireformcontrasts with the cloth cover so as to be visible therethrough.
 7. Thesystem of claim 1, wherein the wireform is made of Nitinol.
 8. Thesystem of claim 1, wherein the cloth cover attaches via a suture to aneyelet provided at the distal end of the access tube.
 9. The system ofclaim 1, wherein the wireform has a proximal portion aligned with theaccess tube that is configured to be manipulated longitudinally from aproximal end of the access tube.
 10. The system of claim 9, wherein thewireform may be retracted from the expanded shape to the compressedshape back into the access tube.
 11. A heart valve annulus sizingsystem, comprising: a compressible Nitinol wireform having an expandedshape of a target heart valve annulus and a compressed shape of smallerprofile; an access tube through which the wireform in its compressedshape may be advanced; and a cloth cover having an inner volume andshape that closely receives the wireform in its expanded shape whenadvanced beyond the access tube.
 12. The system of claim 11, wherein theexpanded shape of the wireform conforms to a mitral annulus and has aconvex posterior side opposite a relatively straight or less convexanterior side.
 13. The system of claim 12, wherein the expanded shape ofthe wireform further includes a pair of trigone notches at theintersections of the posterior and anterior sides, and wherein thewireform is darkly colored to contrast with a light colored cloth cover.14. The system of claim 12, wherein the wireform is radiopaque such thatthe trigones are visible under fluoroscopy.
 15. The system of claim 11,wherein the wireform is configured to expand and assumes a shape withinthe cloth cover that is generally perpendicular to the axis of theaccess tube and to a proximal portion of the wireform that remainswithin the access tube.
 16. The system of claim 15, wherein the wireformforms a generally linear configuration in the compressed shape withinthe access tube.
 17. The system of claim 11, wherein the cloth cover isformed of a diaphanous material and the wireform contrasts with thecloth cover so as to be visible therethrough.
 18. The system of claim11, wherein the cloth cover attaches to the distal end of the accesstube.
 19. The system of claim 17, wherein the cloth cover attaches via asuture to an eyelet provided at the distal end of the access tube. 20.The system of claim 11, wherein the wireform has a proximal portionaligned with the access tube that is configured to be manipulatedlongitudinally from a proximal end of the access tube.